This invention relates generally to the field of telephony, and more particularly to an improved test cord for testing individual subscriber circuits appearing on a telephone main frame in a telephone office. Devices of this general type are known in the art, and the invention lies in specific constructional details which permit improved ease of manufacture, as well as facilitated use by telephone service personnel.
As is known in the art, it is common practice to interconnect incoming subscriber circuits to a telephone main frame, from where they are routed to office switching equipment. The main frame is a convenient point at which to install individual protective devices, usually in the form of a small module to prevent excess current surges which may be present on the subscriber lines from reaching the office equipment and damaging the same. It is usual to provide on a protector block some means of access for test equipment on the main frame as well. Prior art protector blocks, in addition to providing terminals for engaging the protector modules, also provide a separate area or test field at which test equipment in the form of probes may be engaged. Unfortunately, the test field occupies a substantial amount of area on the protector block which would otherwise be better employed to accommodate terminals for additional subscriber circuits. The problem of utilization of existing space on the main frame has been sufficiently serious that protector modules have been developed in which test points are provided on the exposed ends of the modules thereby eliminating the necessity of providing separate test fields and the accompanying utilization of substantial space on the frame. The test points are recessed between small openings in the outer end of the housing of the module and are accessible to service personnel once the proper module is identified.
It is known to provide a plug type multicontact probe which engages the exposed end of the module during the testing procedure. The known types of such construction are in the form of an elongated plug having a cross section corresponding to that of the protector module, and having rigid prongs which engage corresponding openings in the module to effect the necessary contacts. A recess is provided in the forward end of the plug to clear the manually engageable handle on the protector module during the engagement. Because of the purchase obtained on the projecting prongs entering the body of the module, disengagement of the plug from the module after completion of the test procedure is often difficult, and on occasion results in simultaneous disengagement of the protector module from the associated protector block.